1. Field of the Invention
This invention relates generally to tools with extensible handles and, in particular, to an extensible ratchet wrench.
2. Description of the Prior Art
Clothier et al., U.S. Pat. No. 2,963,930 describes an extensible torque bar having an inner shaft with spaced depressions along the shaft, an outer tube, a single ball bearing for communicating through the torque tube to the depressions of the torque bar and a slidable locking sleeve with ball ridge and ball chamber therein, the sleeve being spring biased to constrain the ball within one of the depressions.
In Jeannotre, U.S. Pat. No. 4,070,932 an outer sleeve which supports a tool headpiece at one end thereof is mounted telescopically about an internal rod. The rod has a groove with a longitudinal portion and transverse leg portion. A latch mechanism with an inwardly extending abutment carried by a sleeve secures the rod in its position of extension or retraction by disposing the abutment in one of the transverse leg portions. A coil spring biases the rod towards an outward position.
Newby et al., U.S. Pat. No. 4,376,397 describes an adjustable extension device for tools in which a latch member passes through an outer female member or sleeve into one of a plurality of longitudinally spaced detents in an inner male member or rod.
Shull, U.S. Pat. No. 4,581,958 describes an extensible handle assembly for a ratchet wrench having a tubular handle member with a central hole down its length and a tool engaging shank extending through the central hole. The shank is slidable in the handle member between extended and retracted positions and includes a transverse springloaded detent to engage the shank at each of those positions.
Thomas, U.S. Pat. No. 5,033,337 discloses an extension element for use with wrench type hand tools. The element includes a rectangular bored handle that receives an extension arm which has a plurality of spring loaded ball bearings within transverse spread apart transverse bores. The handle is also provided with a transverse bore. A spring in one of the arm handle bores forces its ball into the handle bore to lock the extension arm in place. The transverse bores give rise to inherent weakness in handle and arm.
In Raber, U.S. Pat. No. 5,109,737, a spring loaded detent in the handle of a ratchet tool is adapted to extend into one of a plurality of aligned holes in a sleeve member. Raber is inherently a weak device structurally. Any undue stress would cause this tool to snap.
Lan, U.S. Pat. No. 5,138,911 is another telescopic wrench extension, but structurally weak due to a longitudinal slot in a telescopic tubular sleeve member.
In Lee, U.S. Pat. No. 5,193,149 the sleeve portion of an extensible wrench includes a transverse hole in its flange portion that goes all the way through creating a weakness in same.
Hillinger, U.S. Pat. No. 5,285,702 describes an extendible tool handle wherein an outer handle member defines an air chamber about an inner handle member.
The prior art devices suffer from inherent structural weakness, limited extendibility and limited choice of lengths.